ed. Parsons, 1836, p. 408). Slingsby entered Queens' College, Cambridge, as a fellow-commoner in January 1618–19, but appears to have left Cambridge without taking a degree, though he resided there till 1621 (ib. vi. 302–18). On 7 July 1631 he married, at Kensington Church, Barbara, daughter of Thomas Bellasyse, first viscount Fauconberg. On 2 March 1638 he was created a baronet of Nova Scotia (ib. p. vii). In the first war with the Scots (1639) he served in Lord Holland's troop, and took part in his famous march to Kelso.
Slingsby represented Knaresborough in both of the two parliaments summoned in 1640, and was one of the fifty-nine members who voted against the attainder of the Earl of Strafford (ib. pp. 50, 63). In his diary he explains that while he supported the bill for removing the bishops from the House of Lords, he was against the abolition of episcopacy. The religious question, and the view that it was unlawful to seek the reformation of the state by arms, concurred in leading him to adopt the king's cause against the parliament (ib. pp. 13, 67). Shortly after Charles came to York, Slingsby was commissioned to command the city regiment of trained bands (11 May 1642), and later (13 Dec. 1642) he received a commission from Lord Newcastle to raise a volunteer regiment of foot (ib. pp. 76, 87). Under Newcastle, Slingsby served through the northern campaigns in 1643 and 1644, fought at the battle of Marston Moor, and marched out of York when it surrendered to Fairfax and the Scots (July 1644). After various adventures he joined the king at Oxford in December 1644, was present at the capture of Leicester and the battle of Naseby, and accompanied Charles in his aimless marches through England after Naseby. In November 1645 he joined the garrison of Newark, and was there at its surrender in May 1646.
Slingsby went home to Redhouse, but found himself at once called upon to take the negative oath and the covenant if he wished to live undisturbed. This he refused to do. ‘The one,’ he wrote, ‘makes me renounce my allegiance, the other my religion.’ He lived in great retirement, long confined to a single room in his own house in order to avoid arrest (Parsons, pp. 119, 179, 332). In 1651 his estate, for which he had refused to compound, since compounding would have involved taking the oaths he abhorred, was ordered to be sold. It was purchased by his relatives, Slingsby Bethel [q. v.] and Robert Stapleton, who held it as trustees for Slingsby and his children (ib. pp. 343–55; Calendar of the Committee for Compounding, 1387). His loyalty was unabated; and, in spite of his pecuniary losses, he lent 100l. to Nicholas Armorer, one of the king's agents in England, and received the king's thanks from Hyde (Cal. Clarendon Papers, ii. 336, 347). In March 1655 he was implicated in the projected royalist rising in Yorkshire, was arrested, and sent to the garrison of Hull to be imprisoned (Thurloe Papers, iv. 462, 468, 614). Unfortunately for himself, he endeavoured to gain over one of the officers of the garrison, Major Waterhouse, thinking that Hull would be an admirable landing-place for Charles II and the troops whom he had got together in Flanders. Waterhouse, by the command of his superiors, listened to Slingsby's overtures, and finally obtained from him a commission signed by Charles II. Two other pseudo-converts to royalism among the officers were also the recipients of Slingsby's confidences. The government, which was anxious to put a stop to the continual plottings of the royalists, resolved to make an example of Slingsby. Accordingly, on 27 April 1658, a commission was issued establishing a high court of justice, under an act passed by the late parliament, and he was tried before it on 25 May following in Westminster Hall. Slingsby at first demanded to be tried by a jury, but finally pleaded not guilty. The evidence of the three witnesses against him was conclusive, and his only defence was that his overtures were made in jest. With more truth he added: ‘I see that I am trepanned by these two fellows. … I never sought to them, but they to me; the commission was procured by no intercourse with any persons beyond the seas, but a blank which I had for four years together.’ This defence was naturally unavailing, and on 2 June he was sentenced to death (State Trials, v. 871; Thurloe Papers, vi. 781). Great efforts were made to save his life by his nephew, Lord Fauconberg, who had recently married Cromwell's daughter, but without result. Slingsby was beheaded on Tower Hill on 8 June. An account of his speech and behaviour on the scaffold is given in ‘Mercurius Politicus’ (3–10 June 1658). A letter which he wrote to a friend after his sentence is printed in the appendix to his ‘Diary’ (ed. Parsons, p. 230). As Ludlow observes in his comments on Slingsby's trial, ‘in the opinion of many men he had very hard measure’ (Memoirs, ii. 40, ed. 1894).
Slingsby's body was given to his family, and he was buried in the Slingsby chapel in Knaresborough Church (Diary, ed. Parsons, p. 412). He left two sons—Thomas, second baronet, who died about 1685; and Henry,
